1. Field of the Invention
The present invention relates to a measuring device for oblique angle which is used to measure an oblique angle of a surface to be measured, to measure precision of motion of an object to be measured, and to measure a flatness of a platen or the like.
2. Description of the Prior Art
It is generally desired that a measuring instrument used when an oblique angle is measured is high in resolution, high in linearity in the range of required measurement and has no hysteresis. In the past, to measure the oblique angle, optical measuring instruments have been used such as an auto-collimater and a laser measuring device, and levels and inclinometers making use of a pendulum.
The optical measuring instruments such as an auto-collimater or laser measuring device make a great error if the measuring range is widely taken. Sometimes, a light projecting and receiving instrument has to be placed on a reference surface independently of a surface to be measured to undergo a spatial restriction. Furthermore, it has not been possible to measure rolling out of precision of motion. In the absolute oblique angle measuring instrument such as an inclinometer or a level, an oblique angle can be measured by mere placement thereof on a surface to be measured, and therefore, it is free from spatial restriction. However, there are disadvantages in that if the resolution is increased, the range of measurement becomes narrow, and if the range of measurement is increased, an error resulting from non-linearity increases.